<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
    div {
      width: 80px;
    }

    input[type=text] {
      width: 50px;
      height: 44px;
      outline: none;
      border: 1px solid #ccc;
      text-align: center;
      border-right: 0;
    }

    input[type=button] {
      height: 24px;
      width: 22px;
      cursor: pointer;
    }

    input {
      float: left;
      border: 1px solid #ccc;

    }
  </style>
</head>

<body>
  <div>
    <input type="text" id="total" value="1" readonly>
    <input type="button" value="+" id="add">
    <input type="button" value="-" id="reduce" disabled>
    <script>
      const total = document.querySelector('#total')
      const btnjia = document.querySelector('#add')
      const btnjian = document.querySelector('#reduce')
      const judge = function () {
        if (total.value > 1) {
          btnjian.disabled = false
        } else {
          btnjian.disabled = true
        }
      }
      btnjia.addEventListener('click', function () {
        total.value++
        judge()
      })
      btnjian.addEventListener('click', function () {
        total.value--
        judge()
      })
    </script>
  </div>
</body>

</html>